Field of Invention
The present invention relates to support linkage arrangements for the mounting of a counterweight to the front of a tractor, and in particular to a top link for use in a three-point support linkage where the lower links are fixed relative to a chassis of the tractor.
Description of Related Art
The continuing trend for agricultural machinery to grow in size goes hand-in-hand with the increasing size and power of tractors. Technical advances have allowed the power of tractors to increase without a proportionate increase in overall weight. In some applications this is advantageous, for example where soil compression is to be avoided. However, in order to transmit the power of the tractor to the ground without excessive wheel slippage, it is known to provide counterweights on either the front or the rear of the tractor depending on the application.
WO 2000/051613 discloses a single-piece tractor weight which can be attached to a front three-point linkage of a tractor by means of a transverse crossbar and a top-link hitching point. The transverse crossbar is supported on the lower links such as to permit the counterweight to pivot about the axis of the crossbar. The pivoting is useful during mounting of the counterweight, whether by simply hanging the counterweight in place by the use of a front loader or fork lift truck or similar, or by having a powered lift mechanism which allows the lower links to be lowered to receive the crossbar and then raised to lift it clear of the ground. However, the pivoting causes problems during normal working if the counterweight can swing such as to impact the chassis or bodywork of the tractor. Some known tractors have a mechanical stop extending from the chassis to constrain the extent of pivoting: the solution preferred in WO 2000/051613 (which has a front powered lift with pivoting lower links to pick up the counterweight) is to use an upper hitch link arrangement which is mounted to the chassis and extends to the top-link hitching point of the counterweight and prevents pivoting.
Problems can occur when mounting the counterweight in aligning the connections for the top link if the counterweight has pivoted out of the desired position, unless the top link is of a more complex variable length construction, for example as a hydraulic cylinder or threaded telescoping arrangement. Problems can also occur when demounting the counterweight if the constrained pivoting action places the top link in compression or tension, either of which can make it difficult to disengage the means (mounting bolts, pins etc.) used to attach the top link to the counterweight.